Liver cirrhosis and portal hypertension will be created in dogs. In this animal model the following investigations will be performed: Vasodilatoric drugs will be tested for their effectiveness to improve arterial portography in portal hypertension. Effect and side effects of intravenous versus selective superior mesenteric artery infusion of vasopressin will be compared and prostoglandin F sub 2 alpha will be investigated for its potential to reduce portal hypertension. Polyvinyl alcohol (Ivalon) will be evaluated as a new agent for permanent occlusion of gastroesophageal varices and an attempt will be made to force the development of spontaneous splenorenal or retroperitoneal shunts by repeatedly occluding all other portosystemic collaterals with this agent. The production of intrahepatic portovenous shunts will be investigated for their feasibility to reduce portal hypertension.